In our work we will simulate the behavior of an exoskeleton with the musculoskeletal simulation software OpenSim. To do this, we first performed initial tests to evaluate the human upper limb model available. Having done this, we have coupled to it the model of an exoskeleton. The BushingForce was used to perform the coupling and, thanks to some tests, the stiffness and damping values that make up this method were evaluated, in order to better reproduce a real behavior. Subsequently the effect of the exoskeleton on humans was evaluated. Evaluating muscle activation during a drilling task. The positive effect of the device was seen, with a significant reduction in the muscle activity.